How much will using headphones increase battery life?
The current necessary to drive a set of headphones is considerably smaller than that required to drive the low impedance speaker. The speakers in most metal detectors are of 8 or 16 ohms impedance, while most detectors use a resistor of approximately 100 to 200 ohms to limit the sound output in the headphones. Using the numbers quoted, a set of headphones should result in an increase of approximately 2 to 3 times the operating life. Since the electronics circuitry is always operating, even though the detector may not be making noise, the savings is not as big as the numbers would indicate.
